16v has more power when motor is cold?

[mkii_84@yahoo.com (Andrew Wong)]

I don't own a 16v, but I noticed that my 2.2l 10v
5cylinder with CIS-E has felt quicker when running
cold, the temperature in FL has been lower than
usually lately and acceration felt better
--- "T. Reed" <treed2@u.washington.edu> wrote:
> Hey all,
> 
> Just got back from a drive tonight and I noticed
> that during the first 2
> minutes or so the car had kick ass power.. I mean, I
> was barely laying in
> to the throttle .. probably just a touch over half
> way, and the tires were
> chirping in 1st and 2nd without even trying. After
> the car was warmed
> up I went over the same stretch of road and while it
> was still fast and
> there was no "huge" reduction in power, I couldn't
> get the tires to chirp
> again with the same amount of throttle. Both times I
> was just doing my
> normal smooth declutching action.
> 
> I know that's not very scientific, but I'm feeling
> like my motor is
> running "torquier" when it hasn't warmed up yet.
> Ambient air temp is about
> 50 F, but I can't imagine that cold vs. warm air
> could make that much of a
> difference, besides.. my engine runs cold to begin
> with (I never get to
> the LED on the water temp gauge)
> 
> I do have my mixture set to 4 mA +/- 1 mA.. Stock is
> 5 mA or 10 mA
> depending on who you ask. This is a 2.0 16v with 1.8
> head, BTW.
> 
> I've noticed that my idle bounces a bit until the
> car warms up. I've heard
> that this can indicate a rich mixture, but I can't
> rememebr why.
> 
> I suspect that what might be happening is while the
> car is in open loop
> mode, the mixture is not influenced by the O2 sensor
> and is going rich
> because of my non-stock mechanical setting of the
> mixture screw. But
> once the car warms up, the oxygen sensor bypasses
> the mechanical setting,
> leaning out the mixture and causing me to loose
> power..
> 
> I replaced the sensor about 1.5 years ago with a
> universal bosch sensor
> and spliced the wires in to the original harness.
> 
> So I'm wondering:
> 
> - what is the difference between euro mechanical CIS
> for 16v's and our
>   CIS-E running in open loop mode? It seems to me
> like there should be no
>   difference.. in steady-state conditions the
> mixture is based completely
>   off of the mechanical adjust screw when in open
> loop mode.. it should
>   be possible to force the car in to open loop (by
> disconnecting the o2
>   sensor) and tune the screw to keep something just
> a little richer than
>   stoich. This would also preserve all the warm-up
> and acceleration
>   enrichment features of CIS-E (assuming they
> normally operate when in
>   open loop)
> 
> - has anyone tried placing a resistor in line with
> the oxygen sensor to
>   cause its output voltage to be divided between the
> resistor and the
>   computer, effectively making the computer "see" a
> lower voltage (which
>   corresponds to a leaner mixture) and thus causing
> it to richen the
>   mixture on its own? It seems like this would
> work.. if it did then you
>   could put a potentiometer in line and tune the
> mixture to your liking,
>   electrically.
> 
> I think I might try the latter, and borrow my
> friend's homemade air fuel
> meter that hooks to the o2 sensor and see if putting
> resistance inline
> is indeed effective in changing the mixture. First,
> though.. I'll need to
> put an ammeter inline with the o2 sensor and see how
> much current is going
> through the circuit so I can determine what range of
> resistance is needed.
> 
> Anyway, I just thought I'd share my ideas about this
> since I know CIS-E is
> notorious for leaning things out in the name of fuel
> economy.
> 
> I've thought about buying one of those euro CIS
> setups for $300-ish but in
> my opinion there is nothing mechanically wrong with
> the CIS-E I already
> have.. its more than capable of delivering the
> amount of fuel (and the
> proper amount, at that).. so why junk it? As an
> electrical engineering
> student I'm inclined to find an electrical (read:
> cheap; components cost
> just pennies and are readily available) solution
> that uses the existing
> mechanical parts and sensors to accomplish the same
> goal.
> 
> -Toby
> 
> 
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=====
-Andrew Wong 
1984 Black Scirocco
1987 White Quantum wagon

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